Kangaroos “box” with their hind feet; not like in cartoons or trained animal acts, where they have boxing gloves on their fore paws (although their front claws are pretty impressive as well!). And they are definitely dangerous. But as long as Tyson can keep from getting disemboweled first, with the daggers on the kangaroos hind feet, if he get’s off the first few right hooks, the ‘roo should be out for the count. Unlike most large clawed animals, although they can and do bite, the kangaroo’s jaws and teeth won’t be a major weapon. So Tyson’s throat won’t be a prime target, as if he was fighting one of the big cats, for instance, although incidental damage to his throat could occur. Tyson’s neck is rather short though, so that will be an advantage. He will come out bloodied, though. It won’t be a walkabout in the park. A large aggressive kangaroo could surely take down many different men. But not all men. I think Tyson would prevail. His professional skills could actually be of use in this situation. And certainly his build and exceptional power don’t hurt either.

EDIT: In answering this question, I’m assuming that the kangaroo in the fight is not a trained “boxing” ‘roo, but rather a strong, untamed, wild animal that has reason to put up a serious fight.